Getting the number of decimal places: Difference between revisions

Content added Content deleted

Inline

Revision as of 12:19, 2 June 2022

Task

Write a program (function) to get the number of decimals in a given number.

Examples

for num = 12.345 decimals = 3, and
for num = 12.3450 decimals = 4

(Note that the reference implementation – in the Ring language – shows a function over a given number rather than a given numeric string, and that the sample values shown above are not enclosed in quotes).

11l

Translation of: Python

<lang 11l>F dec(n)

  R I ‘.’ C n {n.split(‘.’).last.len} E 0

print(dec(‘12.345’)) print(dec(‘12.3450’))</lang>

Output:

3
4

Action!

Library: Action! Tool Kit

<lang Action!>INCLUDE "D2:REAL.ACT" ;from the Action! Tool Kit

BYTE FUNC FindC(CHAR ARRAY s CHAR c)

 BYTE i

 FOR i=1 TO s(0)
 DO
   IF s(i)=c THEN
     RETURN (i)
   FI
 OD

RETURN (0)

BYTE FUNC DecimalCount(REAL POINTER r)

 CHAR ARRAY s(20),sub(20)
 BYTE i,dotPos,ePos,count
 INT exp

 StrR(r,s)
 ePos=FindC(s,'E)
 IF ePos>0 THEN
   ePos==+1
   IF s(ePos)='+ THEN
     ePos==+1
   FI
   SCopyS(sub,s,ePos,s(0))
   exp=ValI(sub)
 ELSE
   exp=0
 FI
 dotPos=FindC(s,'.)
 count=0
 IF dotPos>0 THEN
   FOR i=dotPos+1 TO s(0)
   DO
     IF s(i)<'0 OR s(i)>'9 THEN
       EXIT
     FI
     count==+1
   OD
 FI
 IF exp<0 THEN
   count==-exp
 ELSEIF exp<count THEN
   count==-exp
 ELSE
   count=0
 FI

RETURN (count)

PROC Test(REAL POINTER r)

 BYTE count

 count=DecimalCount(r)
 PrintR(r)
 PrintF(" has %I decimals%E",count)

RETURN

PROC Main()

 REAL r

 Put(125) PutE() ;clear screen
 ValR("1234",r) Test(r)
 ValR("123.4",r) Test(r)
 ValR("12.34",r) Test(r)
 ValR("1.234",r) Test(r)
 ValR("0.1234",r) Test(r)
 ValR("1.234E-3",r) Test(r)
 ValR("1.234E-10",r) Test(r)
 ValR("1.E-10",r) Test(r)
 ValR("1.23456789E10",r) Test(r)

RETURN</lang>

Output:

Screenshot from Atari 8-bit computer

1234 has 0 decimals
123.4 has 1 decimals
12.34 has 2 decimals
1.234 has 3 decimals
.1234 has 4 decimals
1.234E-03 has 6 decimals
1.234E-10 has 13 decimals
1E-10 has 10 decimals
1.23456789E+10 has 0 decimals

AutoHotkey

<lang AutoHotkey>for i, v in [10, "10", 12.345, "12.345", 12.3450, "12.3450"] output .= v " has " StrLen(StrSplit(v, ".").2) " decimals.`n" MsgBox % output</lang>

Output:

10 has 0 decimals.
10 has 0 decimals.
12.345 has 3 decimals.
12.345 has 3 decimals.
12.3450 has 4 decimals.
12.3450 has 4 decimals.

AWK

syntax: GAWK -f GETTING_THE_NUMBER_OF_DECIMALS.AWK

BEGIN {

   n = split("10,1.,1.0,12.345,12.3450",arr,",")
   for (i=1; i<=n; i++) {
     s = arr[i]
     x = index(s,".")
     printf("%s has %d decimals\n",s,x?length(s)-x:x)
   }
   exit(0)

} </lang>

Output:

10 has 0 decimals
1. has 0 decimals
1.0 has 1 decimals
12.345 has 3 decimals
12.3450 has 4 decimals

C

<lang c>#include <stdio.h>

int findNumOfDec(double x) {

   char buffer[128];
   int pos, num;

   sprintf(buffer, "%.14f", x);

   pos = 0;
   num = 0;
   while (buffer[pos] != 0 && buffer[pos] != '.') {
       pos++;
   }
   if (buffer[pos] != 0) {
       pos++; // skip over the decimal
       while (buffer[pos] != 0) {
           pos++; // find the end of the string
       }
       pos--; //reverse past the null sentiel
       while (buffer[pos] == '0') {
           pos--; // reverse past any zeros
       }
       while (buffer[pos] != '.') {
           num++;
           pos--; // only count decimals from this point
       }
   }
   return num;

}

void test(double x) {

   int num = findNumOfDec(x);
   printf("%f has %d decimals\n", x, num);

}

int main() {

   test(12.0);
   test(12.345);
   test(12.345555555555);
   test(12.3450);
   test(12.34555555555555555555);
   test(1.2345e+54);
   return 0;

}</lang>

Output:

12.000000 has 0 decimals
12.345000 has 3 decimals
12.345556 has 12 decimals
12.345000 has 3 decimals
12.345556 has 14 decimals
1234500000000000060751116919315055127939946206157864960.000000 has 0 decimals

C++

Translation of: C

<lang cpp>#include <iomanip>

include <iostream>
include <sstream>

int findNumOfDec(double x) {

   std::stringstream ss;
   ss << std::fixed << std::setprecision(14) << x;

   auto s = ss.str();
   auto pos = s.find('.');
   if (pos == std::string::npos) {
       return 0;
   }

   auto tail = s.find_last_not_of('0');

   return tail - pos;

}

void test(double x) {

   std::cout << x << " has " << findNumOfDec(x) << " decimals\n";

}

int main() {

   test(12.0);
   test(12.345);
   test(12.345555555555);
   test(12.3450);
   test(12.34555555555555555555);
   test(1.2345e+54);
   return 0;

}</lang>

Output:

12 has 0 decimals
12.345 has 3 decimals
12.3456 has 12 decimals
12.345 has 3 decimals
12.3456 has 14 decimals
1.2345e+54 has 0 decimals

FreeBASIC

<lang freebasic>Function dec(n As Double) As Uinteger

   Dim As String c = Str(n)
   Return Iif(Instr(c, "."), Len(Mid(c,Instr(c, ".")+1)), 0)

End Function

Dim As Double n(1 To ...) => {7, 12.00, 12.345, 12.345677, 0.142857142857142}

For i As Integer = 1 To Ubound(n)

   Print n(i); " has "; dec(n(i)); " decimals"

Next i Sleep</lang>

Output:

 7 has 0 decimals
 12 has 0 decimals
 12.345 has 3 decimals
 12.345677 has 6 decimals
 0.142857142857142 has 15 decimals

Go

Translation of: Wren

<lang go>package main

import (

   "fmt"
   "log"
   "math"
   "strings"

)

var error = "Argument must be a numeric literal or a decimal numeric string."

func getNumDecimals(n interface{}) int {

   switch v := n.(type) {
   case int:
       return 0
   case float64:
       if v == math.Trunc(v) {
           return 0
       }
       s := fmt.Sprintf("%g", v)
       return len(strings.Split(s, ".")[1])
   case string:
       if v == "" {
           log.Fatal(error)
       }
       if v[0] == '+' || v[0] == '-' {
           v = v[1:]
       }
       for _, c := range v {
           if strings.IndexRune("0123456789.", c) == -1 {
               log.Fatal(error)
           }
       }
       s := strings.Split(v, ".")
       ls := len(s)
       if ls == 1 {
           return 0
       } else if ls == 2 {
           return len(s[1])
       } else {
           log.Fatal("Too many decimal points")
       }
   default:
       log.Fatal(error)
   }
   return 0

}

func main() {

   var a = []interface{}{12, 12.345, 12.345555555555, "12.3450", "12.34555555555555555555", 12.345e53}
   for _, n := range a {
       d := getNumDecimals(n)
       switch v := n.(type) {
       case string:
           fmt.Printf("%q has %d decimals\n", v, d)
       case float32, float64:
           fmt.Printf("%g has %d decimals\n", v, d)
       default:
           fmt.Printf("%d has %d decimals\n", v, d)
       }
   }

}</lang>

Output:

12 has 0 decimals
12.345 has 3 decimals
12.345555555555 has 12 decimals
"12.3450" has 4 decimals
"12.34555555555555555555" has 20 decimals
1.2345e+54 has 0 decimals

Haskell

<lang Haskell>decimal :: String -> Int decimal [] = 0 decimal ('.':xs) = length xs decimal (_:xs) = decimal xs

numDecimal :: Double -> Int numDecimal = decimal . show

main = print . map numDecimal $ [12.0, 12.345, 12.3450, 12.345555555555, 12.34555555555555555555, 1.2345e+54]</lang>

Output:

[1,3,3,12,15,7]

Java

<lang java>public static int findNumOfDec(double x){

   String str = String.valueOf(x);
   if(str.endsWith(".0")) return 0;
   else return (str.substring(str.indexOf('.')).length() - 1);

}</lang>

Julia

<lang julia>function postprecision(str::String)

   s = lowercase(str)
   if 'e' in s
       s, ex = split(s, "e")
       expdig = parse(Int, ex)
   else
       expdig = 0
   end
   dig = something(findfirst('.', reverse(s)), 1) - 1 - expdig
   return dig > 0 ? dig : 0

end

postprecision(x::Integer) = 0 postprecision(x::Real, max=22) = postprecision(string(round(Float64(x), digits=max)))

testnums = ["0.00100", 0.00100, 001.805, 1.0 / 3, 2//3, 12, 12.345, "12.3450",

   "12.34555555555555555555", 1.2345e+54, 1.2345e-08, "1.2345e-08", π]

for n in testnums

   println("$n has $(postprecision(n)) decimals.")

end

</lang>

Output:

0.00100 has 5 decimals.
0.001 has 3 decimals.
1.805 has 3 decimals.
0.3333333333333333 has 16 decimals.
2//3 has 16 decimals.
12 has 0 decimals.
12.345 has 3 decimals.
12.3450 has 4 decimals.
12.34555555555555555555 has 20 decimals.
1.2345e54 has 0 decimals.
1.2345e-8 has 12 decimals.
1.2345e-08 has 12 decimals.
π has 15 decimals.

Kotlin

Translation of: Java

<lang scala>fun findNumOfDec(x: Double): Int {

   val str = x.toString()
   if (str.endsWith(".0")) {
       return 0
   }
   return str.substring(str.indexOf('.')).length - 1

}

fun main() {

   for (n in listOf(12.0, 12.345, 12.345555555555, 12.3450, 12.34555555555555555555, 1.2345e+54)) {
       println("%f has %d decimals".format(n, findNumOfDec(n)))
   }

}</lang>

Output:

12.000000 has 0 decimals
12.345000 has 3 decimals
12.345556 has 12 decimals
12.345000 has 3 decimals
12.345556 has 15 decimals
1234500000000000000000000000000000000000000000000000000.000000 has 7 decimals

Lambdatalk

In lambdatalk numbers are words/strings, some operators, like "+,-,*,/,...", know what to do with words like "123". <lang Scheme> {W.length

{S.replace 0 by in
 {S.rest   
  {S.replace \. by space in 12.3456000}}}}

-> 4 </lang>

Perl

Need pragma bignum to handle decimals beyond 15 digits. <lang perl>use bignum;

printf "Fractional precision: %2s Number: %s\n", length((split /\./, $_)[1]) // 0, $_

   for 9, 12.345, <12.3450>, 0.1234567890987654321, 1/3, 1.5**63;</lang>

Output:

Fractional precision:  0  Number: 9
Fractional precision:  3  Number: 12.345
Fractional precision:  4  Number: 12.3450
Fractional precision: 19  Number: 0.1234567890987654321
Fractional precision: 40  Number: 0.3333333333333333333333333333333333333333
Fractional precision: 63  Number: 124093581919.648947697827373650380188008224280338254175148904323577880859375

Phix

constant fracfmt = iff(machine_bits()=32?"%.14g":"%.18g")
 
function num_decimals(object o)
    integer nd = -1
    string s, t
    if integer(o) then
        nd = 0
        s = sprintf("%d",o)
    elsif atom(o) then
        s = sprintf("%.19g",o)
        o -= trunc(o)
        if o=0 then
            nd = 0
        else
            t = sprintf(fracfmt,o)
        end if
    elsif string(o) then
        s = o
        t = s
    else
        crash("unknown type")
    end if
    if nd=-1 then
        integer e = find('e',t)
        if e then
            {t,e} = {t[1..e-1],to_number(t[e+1..$])}
        end if
        integer dot = find('.',t)
        nd = iff(dot?max(length(t)-dot-e,0):max(-e,0))
    end if
    s = shorten(s,"digits",5)
    return {s,nd}
end function
 
sequence tests = {"0.00100", 0.00100, 001.805, 1/3, 12, 12.345, 12.345555555555, 
                  "12.3450", "12.34555555555555555555", 12.345e53, 1.2345e-08, 
                  "12.345e53", "1.2345e-08", "0.1234567890987654321",
"124093581919.648947697827373650380188008224280338254175148904323577880859375"}
 
for i=1 to length(tests) do
    printf(1,"%25s has %d decimals\n",num_decimals(tests[i]))
end for

Output:

32 bit

                  0.00100 has 5 decimals
                    0.001 has 3 decimals
                    1.805 has 3 decimals
       0.3333333333333333 has 14 decimals
                       12 has 0 decimals
                   12.345 has 3 decimals
          12.345555555555 has 12 decimals
                  12.3450 has 4 decimals
  12.34555555555555555555 has 20 decimals
               1.2345e+54 has 0 decimals
                1.2345e-8 has 12 decimals
                12.345e53 has 0 decimals
               1.2345e-08 has 12 decimals
    0.1234567890987654321 has 19 decimals
12409...59375 (76 digits) has 63 decimals

64 bit as above except

    0.3333333333333333333 has 18 decimals

Python

Treated as a function over a string representation of a number to allow the capturing of significant trailing zeros. <lang python>In [6]: def dec(n):

  ...:     return len(n.rsplit('.')[-1]) if '.' in n else 0

In [7]: dec('12.345') Out[7]: 3

In [8]: dec('12.3450') Out[8]: 4

In [9]: </lang>

Or, defining a slightly less partial function, over a given number, rather than a string:

<lang python>Report the decimal counts in default stringifications.

import math

decimalCount :: Num -> Either String (Int, Int)

def decimalCount(n):

   Either a message string, or a tuple
      giving the number of decimals in the default
      (repr) representations of the real
      (and any imaginary part) of the given number.
   
   # decimalLen :: Float -> Int
   def decimalLen(f):
       return len(repr(f).split('.')[-1])

   return Right(
       (0, 0) if isinstance(n, int) else (
           (decimalLen(n), 0)
       ) if isinstance(n, float) else (
           tuple(decimalLen(x) for x in [n.real, n.imag])
       )
   ) if isinstance(n, (float, complex, int)) else (
       Left(repr(n) + ' is not a float, complex or int')
   )

-------------------------- TEST --------------------------
main :: IO ()

def main():

   Counts of decimals in default stringifications of
      real (and any imaginary) components of various
      Python numeric values.
   
   print(fTable(
       'Decimal counts in stringifications of real and imaginary components:'
   )(repr)(
       either(identity)(repr)
   )(decimalCount)([
       7, 1.25, 1.23456e2,
       1 / 7,
       2 ** 0.5,
       math.pi, math.e,
       complex(1.23, 4.567),
       None
   ]))

------------------------ GENERIC -------------------------

Left :: a -> Either a b

def Left(x):

   Constructor for an empty Either (option type) value
      with an associated string.
   
   return {'type': 'Either', 'Right': None, 'Left': x}

Right :: b -> Either a b

def Right(x):

   Constructor for a populated Either (option type) value
   return {'type': 'Either', 'Left': None, 'Right': x}

either :: (a -> c) -> (b -> c) -> Either a b -> c

def either(fl):

   The application of fl to e if e is a Left value,
      or the application of fr to e if e is a Right value.
   
   return lambda fr: lambda e: fl(e['Left']) if (
       None is e['Right']
   ) else fr(e['Right'])

identity :: a -> a

def identity(x):

   The identity function.
   return x

------------------------ DISPLAY -------------------------

fTable :: String -> (a -> String) ->
(b -> String) -> (a -> b) -> [a] -> String

def fTable(s):

   Heading -> x display function -> fx display function ->
      f -> xs -> tabular string.
   
   def gox(xShow):
       def gofx(fxShow):
           def gof(f):
               def goxs(xs):
                   ys = [xShow(x) for x in xs]
                   w = max(map(len, ys))

                   def arrowed(x, y):
                       return y.rjust(w, ' ') + ' -> ' + fxShow(f(x))
                   return s + '\n' + '\n'.join(
                       map(arrowed, xs, ys)
                   )
               return goxs
           return gof
       return gofx
   return gox

MAIN ---

if __name__ == '__main__':

   main()</lang>

Output:

Decimal counts in stringifications of real and imaginary components:
                  7 -> (0, 0)
               1.25 -> (2, 0)
            123.456 -> (3, 0)
0.14285714285714285 -> (17, 0)
 1.4142135623730951 -> (16, 0)
  3.141592653589793 -> (15, 0)
  2.718281828459045 -> (15, 0)
      (1.23+4.567j) -> (2, 3)
               None -> None is not a float, complex or int

Raku

Works with: Rakudo version 2020.07

Raku does not specifically have a "decimal" number type, however we can easily determine the fractional precision of a rational number. It is somewhat touchy-feely for floating point numbers; (what is the fractional precision for 2.45e-12?), it's pretty pointless for Integers; (zero, aalllways zero...), but Rats (rationals) are doable. Note that these are (mostly) actual numerics, not numeric strings. The exception is '12.3450'. That is a numeric string since actual numerics automatically truncate non-significant trailing zeros. If you want to retain them, you need to pass the value as a string. (As below.)

<lang perl6>use Rat::Precise;

printf "Fractional precision: %-2s || Number: %s\n", (.split('.')[1] // ).chars, $_

   for 9, 12.345, '12.3450', 0.1234567890987654321, (1.5**63).precise;

</lang>

Output:

Fractional precision: 0  || Number: 9
Fractional precision: 3  || Number: 12.345
Fractional precision: 4  || Number: 12.3450
Fractional precision: 19 || Number: 0.1234567890987654321
Fractional precision: 63 || Number: 124093581919.648947697827373650380188008224280338254175148904323577880859375

REXX

Since the REXX language stores numbers as strings, the issue of trailing zeros is a moot point.
If the number (as specified) has trailing zeros, there are left intact.

I took it to mean that the number of decimal digits past the decimal point are to be counted and displayed.

Any number specified in exponential notation is first converted to a whole or fractional integer (or an integer with scale),
and that number is then examined. <lang rexx>/*REXX pgm counts number of decimal digits which are to the right of the decimal point. */ numeric digits 1000 /*ensure enuf dec digs for calculations*/ @.=; /*initialize a stemmed array to nulls. */ parse arg @.1; if @.1= then do; #= 9 /*#: is the number of default numbers.*/

                               @.1 = 12
                               @.2 = 12.345
                               @.3 = 12.345555555555
                               @.4 = 12.3450
                               @.5 = 12.34555555555555555555
                               @.6 = 1.2345e+54
                               @.7 = 1.2345e-54
                               @.8 = 0.1234567890987654321
                               @.9 = 1.5 ** 63  /*calculate  1.5  raised to 63rd power.*/
                               end
                          else #= 1             /*the # of numbers specified on the CL.*/

say 'fractional' say ' decimals ' center("number", 75) say '══════════' copies("═", 75)

         do j=1  for #;    n= countDec(@.j)     /*obtain the number of fractional digs.*/
         say right(n, 5)   left(,4)  @.j      /*show # of fract. digits & original #.*/
         end   /*j*/

exit 0 /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ countDec: procedure; parse upper arg x /*obtain a number from the invoker. */

         if pos('E', x)>0  then do              /*handle if the number has an exponent.*/
                                LX= length(x)           /*length of the original number*/
                                parse var x 'E' expon   /*obtain the exponent.         */
                                LE= length(LE)          /*the length of the exponent.  */
                                numeric digits LX + LE  /*ensure enough decimal digits.*/
                                x= format(x, , , 0)     /*REXX does the heavy lifting. */
                                end
         parse var x '.' fract                  /*parse number, get the fractional part*/
         return length(fract)                   /*return number of fractional digits.  */</lang>

output when using the default inputs:

fractional
 decimals                                    number
══════════ ═══════════════════════════════════════════════════════════════════════════
    0      12
    3      12.345
   12      12.345555555555
    4      12.3450
   20      12.34555555555555555555
    0      1.2345E+54
   58      1.2345E-54
   19      0.1234567890987654321
   63      124093581919.648947697827373650380188008224280338254175148904323577880859375

Ring

Testing the function

decimals(2) # Unsensitive to the default setting of decimals n = 5.1945 ? NbrOfDecimals(n) # Gives 4

func NbrOfDecimals(n) nTemp = 1 nNbrOfDecimals = 0 while True if nNbrOfDecimals < 9 nNbrOfDecimals++ nTemp *= 10 nTemp1 = n * nTemp - ceil( n * nTemp ) if nTemp1 = 0 return nNbrOfDecimals ok else raise("Acceeding the maximum number of 9 decimals!") ok end </lang>

Output:

Sidef

<lang ruby>func number_of_decimals(n, limit = 1e5) {

   var prec = Num(Num!PREC)>>2
   var prev =

   n = Number(n) if !n.kind_of(Number)

   loop {
       var str = n.as_dec(prec)

       if (prev == str) {
           return (str.contains('.') ? str.substr(str.index('.')+1).len : 0)
       }

       prev = str
       prec *= 2
       return Inf if (prec > limit)
   }

}

var list = [

   9, 12.345, "12.3450", "12.345e53",
   12.34555555555555555555, 0.1234567890987654321,
   Num.pi, 1/3, 1.5**63

]

list.each {|n|

   var c = number_of_decimals(n)
   say "Number of decimals: #{'%3s' % c}  Number: #{n}"

}</lang>

Output:

Number of decimals:   0  Number: 9
Number of decimals:   3  Number: 12.345
Number of decimals:   3  Number: 12.3450
Number of decimals:   0  Number: 12.345e53
Number of decimals:  20  Number: 12.34555555555555555555
Number of decimals:  19  Number: 0.1234567890987654321
Number of decimals: 188  Number: 3.14159265358979323846264338327950288419716939938
Number of decimals: Inf  Number: 0.333333333333333333333333333333333333333333333333
Number of decimals:  63  Number: 124093581919.6489476978273736503801880082242803382541751489

Wren

In the following script, the fourth and fifth examples need to be expressed as strings to avoid getting the wrong answer. If we use numbers instead, trailing zeros will be automatically removed and the result will be rounded to 14 significant figures when stringified or printed.

Converting the fourth example to a Rat or BigRat object wouldn't help as the constructor for those classes automatically reduces the numerator and denominator to their lowest terms. BigRat would work for the fifth example but the argument would have to be passed as a string anyway so we might as well just parse the string. <lang ecmascript>var error = "Argument must be a number or a decimal numeric string."

var getNumDecimals = Fn.new { |n|

   if (n is Num) {
       if (n.isInteger) return 0
       n = n.toString
   } else if (n is String) {
       if (n == "") Fiber.abort(error)
       if (n[0] == "+" || n[0] == "-") n = n[1..-1]
       if (!n.all { |c| "0123456789.".contains(c) }) Fiber.abort(error)
   } else {
       Fiber.abort(error)
   }
   var s = n.split(".")
   var c = s.count
   return (c == 1) ? 0 : (c == 2) ? s[1].count : Fiber.abort("Too many decimal points.")

}

var a = [12, 12.345, 12.345555555555, "12.3450", "12.34555555555555555555", 12.345e53] for (n in a) {

   var d = getNumDecimals.call(n)
   var ns = (n is String) ? "\"%(n)\"" : "%(n)" 
   System.print("%(ns) has %(d) decimals")

}</lang>

Output:

12 has 0 decimals
12.345 has 3 decimals
12.345555555555 has 12 decimals
"12.3450" has 4 decimals
"12.34555555555555555555" has 20 decimals
1.2345e+54 has 0 decimals